1. Technical Field
The present invention relates to an exposure apparatus, an image forming apparatus, and a hologram recording apparatus.
2. Related Art
There has been proposed a printing apparatus including plural switching elements each of which converts a laser beam emitted from a laser light source into a spot beam and plural holographic optical elements each of which causes the spot beam to converge, and the switching elements and the holographic optical elements are provided in correspondence with each other.
There has also been proposed an exposure apparatus including plural light-emitting devices, a first lens array, and a second lens array. The plural light-emitting devices are arrayed on a light source substrate. The first lens array includes plural diffraction positive lenses each of which diffracts transmitted light to cause beams of the light to converge, thereby forming an image. The second lens array includes plural lenses. The first lens array is sandwiched between the second lens array and the plural light-emitting devices. The plural diffraction positive lenses are respectively superimposed with the plural light-emitting devices in a direction perpendicular to the light source substrate.
There has also been proposed an optical writing apparatus, in which an image is divided into many micro pixels, one or plural light sources emit light beams having an intensity corresponding to a density of each pixel, and an image recording medium is scanned with a bright point of the light beam to sequentially expose each pixel region, thereby writing the image. The image recording medium is irradiated with light having a light quantity density that is equal to or more than a threshold, the image recording medium is exposed to form a latent image by a surface potential change or a chemical change or the image recording medium is exposed to form an image having a density change. In the optical writing apparatus, units as many as the pixels are arrayed in a fast-scanning direction. One unit includes a light converging element, a micro optical aperture, a collimator, and a holographic optical element, which are arranged sequentially from the light source side between the light source and the image recording medium. The light converging element causes the light beams to converge. The optical aperture is provided at a position at which the light beam converges. The collimator forms the light beam outgoing from the optical aperture into a substantially parallel light beam. The holographic optical element radiates the light beam while splitting the light beam into plural directions, and the holographic optical element causes the plural light beams to converge onto substantially the same plane.
An object of the invention is to provide, in an exposure apparatus in which beams emitted from plural light-emitting devices formed on a substrate are converged by a hologram to form converged beam spots arranged in a line on an exposed surface, an exposure apparatus that may obtain a line including a desired number of beam spots (light collecting points) at the exposed surface, even if a portion of the plural light-emitting devices is defective. Another object of the invention is to provide an image forming apparatus in which the exposure apparatus is used. A further object of the invention is to provide a hologram recording apparatus that records a hologram in a hologram recording layer in the process of producing the exposure apparatus.